GCN Circular 20378
P. D'Avanzo (INAF-OAB), A. Melandri (INAF-OAB), K. L. Page (U Leicester), D. M. Palmer (LANL) and B. Sbarufatti (INAF-OAB/PSU) report on behalf of the Swift Team: At 08:31:01 UT, the Swift Burst Alert Telescope (BAT) detected a peak in a waiting mode image at a location near to the known source SS Cyg (trigger=730513). Swift slewed immediately to the location. The BAT on-board calculated location is RA, Dec 325.783, +43.422 which is RA(J2000) = 21h 43m 08s Dec(J2000) = +43d 25' 17" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve shows no obvious activity. The XRT began observing the field at 08:33:34.4 UT, 152.9 seconds after the BAT trigger. No source was detected in 461 s of promptly downlinked data. UVOT took a finding chart exposure of 250 seconds with the U filter starting 153 seconds after the BAT trigger. No credible afterglow candidate has been found in the initial data products. The 2.7'x2.7' sub-image covers 25% of the BAT error circle. The typical 3-sigma upper limit has been about 19.2 mag. The 8'x8' region for the list of sources generated on-board covers 100% of the BAT error circle. The list of sources is typically complete to about 18.0 mag. No correction has been made for the expected extinction corresponding to E(B-V) of 0.46. Swift followed up on this image peak despite its low significance (5.9 sigma) due to its rough proximity to a known source. However, the 10 arcmin offset is well outside the error radius for this point source. This, combined with the lack of an BAT rate trigger or an X-ray detection, leads us to conclude that this was a statistical fluctuation in the image plane and not an astrophysical event.